Microwave Performance of Double δ-Doped High Electron Mobility Transistor With Various Lower/Upper Planar-Doped Ratio Designs

The microwave noise, power, and linearity characteristics of pseudomorphic high electron mobility transistors (pHEMTs) with various lower/upper planar delta-doped ratios were systematically evaluated and studied. By varying the lower/upper delta-doped ratio from 1:1 to 1:4, both Schottky gate turn-on voltage V_ON and breakdown voltage V_BR were reduced. In addition, higher upper delta-doped design is effective in improving the device current density, transconductance, output power, and power-added efficiency; however, this design also scarified the flatness of transconductance distribution and Schottky performance, resulting in a degradation of device linearity. As to the noise performance, after increasing the upper delta-doped concentration by more than 2 times 10¹² cm^-2, the minimum noise figure NF_min can be reduced to a stable range, and higher current density cannot efficiently improve the noise performance. Although the 1:4 design provided the largest power density of pHEMT, its high gate leakage current at high input power swing limited its linearity, and 1:3 design achieved the best linearity performance.     

Noise characteristics of InGaP-gated PHEMTs under high current and thermal accelerated stresses

The degradation mechanisms of the noise characteristics of InGaP-gated low-noise pseudomorphic high-electron mobility transistors (PHEMTs) under accelerated stresses through dc and thermal stresses are investigated. The devices used were metal-organic chemical vapor deposition-grown In/sub 0.49/Ga/sub 0.51/P/In/sub 0.15/Ga/sub 0.85/As/GaAs low noise PHEMT structures with the gate dimensions of 0.25/spl times/160 /spl mu/m/sup 2/. The key noise/effect parameters of devices including 1) related to the deep-trap behavior in device, 2) source/gate resistances, and 3) gate to source capacitance and intrinsic transconductance are discussed. Based on the dc characteristics under dc and thermal stresses, the variations of the current-voltage curve, the diode characteristics (Schottky gate) with related trapping/detrapping phenomena induced by impact ionization and the variation of the depletion in gate-drain region are also investigated. The high reliability of InGaP low noise PHEMTs is demonstrated by the extremely small variations of the minimum noise figure and the associated power gain at 12 GHz after dc and thermal stresses.     

Investigation of Bulk and DTMOS triple-gate devices under 60 MeV proton irradiation

In this paper, the influence of proton irradiation is experimentally studied in triple-gate Bulk FinFETs with and without Dynamic Threshold MOS configuration (DTMOS). The drain current, transconductance, Drain Induced Barrier Lowering (DIBL) and the important figures of merit for the analog performance such as transconductance-over-drain current, output conductance and intrinsic voltage gain will be compared. Furthermore, the Low-Frequency (LF) noise will be also analyzed in the DT mode and the standard biasing configuration. The results indicate that the better electrical characteristics and analog performance of DTMOS FinFETs make them very competitive candidates for low-noise RF analog applications in a radiation environment.     

A low-frequency noise study of hot-carrier stressing effects in submicron Si p-MOSFETs

This paper reports on the effect of hot-carrier (HC) stress on the static and low-frequency (LF) noise characteristics of p-MOSFETs, fabricated in a 0.7 μm CMOS technology. The impact of the HC degradation is studied as a function of the effective device length L_eff. It is shown that the LF noise spectral density increases up to 20 times faster than the transconductance in linear operation and is much more pronounced for the shortest devices under test. The device parameters are found to degrade according to a 1/L^ν_eff power law, with ν larger than 1.     

Low-frequency noise behavior of Si NMOSTs stressed at 4.2 K

The low-frequency (LF) noise behavior of Si NMOSTs stressed at 4.2 K is investigated and compared with the stress-induced changes in the DC parameters. In linear operation, a reduction of the noise spectral density is observed, which can be explained by considering the reduction in the device transconductance. The excess noise, typically observed in the kink region, is reduced after stress, as is the noise hysteresis. This behaviour can be understood by substituting the changes in the substrate current characteristic in the excess-noise model derived     

Thermal stability of MISFET with low-temp molecular-beamepitaxy-grown GaAs and Al0.3Ga0.7As gate ins

GaAs and Al_0.3Ga_0.7As epilayers grown at LT by MBE were used as insulators in the fabrication of MISFET devices. Parametric changes were used to evaluate the thermal stability of MISFET, to identify failure mechanisms and validate the reliability of these devices. The LT-Al_0.3Ga_0.7As MISFET showed superior thermal stability. The degradation in the performance of MISFET with 1000 Å thick LT-GaAs gate insulator was worse than those of the MESFET. On the other hand, MISFET with 250 Å thick LT-GaAs gate insulators exhibited stable characteristics with thermal stressing, LF (low frequency) noise studies on the TLM structures of MISFET layers exhibited 1/f noise in the LT-Al_0.3Ga_0.7As samples and 250 Å LT-GaAs samples; whereas the 1000 Å thick LT-GaAs samples exhibited 1/f^3/2 noise, which was attributed to: (i) the thermal noise generated at the interface of the insulator, and (ii) the active layer due to the outdiffused metallic arsenic. Reverse gate-drain current degradation experiments were carried out at 120°C, 160°C, 200°C, and 240°C. Transconductance frequency dispersion studies were carried out before and after thermal stress on these MISFET. The transconductance of MISFET with 1000 Å LT-GaAs gate insulators was degraded by 40% at 100 kHz after thermal stress. The rest of the samples exhibited stable characteristics. These results indicate that composition changes had occurred at the interface in thicker LT-GaAs MISFET structures. Thinner LT-layers are ideal for achieving higher transconductance and better thermal stability without sacrificing the power capability of MISFET     

高温及关态应力条件下GaAs pHEMT器件的性能退化研究

研究了高温和电学应力下砷化镓赝晶高电子迁移率晶体管的直流特性退化机理。高温下陷阱辅助发射电流引起器件关态漏电上升,而载流子迁移率的退化引起跨导降低;当温度达到450 K时,栅金属的沉降效应会导致跨导异常升高。进一步研究了不同温度下关态电学应力对器件性能退化的影响,结果与高温下栅沉降效应相吻合。     

0.1-µm Gate-length pseudomorphic HEMT's

AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistors (HEMT's) with a gate length of 0.1 µm have been successfully fabricated. The HEMT's exhibit a maximum transconductance of 540 mS/mm with excellent pinch-off characteristics. A maximum stable gain (MSG) as high as 18.2 dB was measured at 18 GHz. At 60 GHz the device has demonstrated a minimum noise figure of 2.4 dB with an associated gain of ∼6 dB. These are the best gain and noise results reported to date for HEMT's.     

耗尽型选择性掺杂异质结晶体管

设计和研制了耗尽型选择性掺杂异质结晶体管。外延选择性掺杂材料是由本所Fs-Ⅲ型分子束外延炉生长的。制作器件的材料在室温下,霍尔测量的电子迁移率为6500cm2/vs,二维薄层电子浓度ns=91011cm2。在77K时n=75000cm2/vs。测量了具有栅长1.21.5m,栅宽2180m耗尽型异质结器件的直流特性和器件的跨导,室温下gm=110～130ms/mm,而低温77K时,可达到200ms/mm。     

50-Å gate-Oxide MOSFET's at 77 K

While hot-carrier-induced degradation is aggravated at cryogenic temperature, a very thin gate-oxide (52-Å) device can still tolerate a 3-V power-supply voltage at 77 K. Hot-carrier-induced degradation may not be the limiting factor in choosing the power-supply voltage and special drain structures may be necessary for very thin gate MOSFET's even at 77 K. However, mobility reduction at high VGis more severe both at lower temperatures and for thinner oxides. Electron mobility appears to be oxide-thickness-dependent at 77 K. The dependence of the electron mobility on the normal field is so strong that it results in unusual I-V characteristics such as negative transconductance at 77 K for an oxide field above 3 MV/cm. The I--V characteristics have been modeled with a mobility dependence on VGSof the form µn ∞ (1 + η(VGS- Vt/Tox)²+ (E/Ec))^-1for 52-Å devices.     

Low-Frequency Noise Characteristics in Strained-Si nMOSFETs

The low-frequency (LF) (1/f) noise mechanism of strained-Si nMOSFETs grown on relaxed Si_1-xGe_x virtual substrates (VSs) has been investigated. It is found that the Si-cap thickness plays an important role in characterizing the 1/f noise mechanism. Ge out-diffusion effect and slight strain relaxation in Si-cap layer are responsible for the degradation of 1/f noise in strained-Si device with 10- and 20-nm-thick Si-cap, respectively. In addition, by choosing proper Si-cap thickness, experimental result shows that as Si-cap undergoes stronger tensile strain for higher Ge concentration VS, the correlated mobility fluctuation term in the modified carrier-number fluctuation model is more dominated for the 1/f noise     

Low-frequency noise in hot-carrier degraded nMOSFETs

This paper discusses the low-frequency (LF) noise in submicron nMOSFETs under controlled transistor aging by hot-carrier stress. Both traditional, steady-state LF noise as well as the LF noise under periodic large-signal excitation were found to increase upon device degradation, for both hydrogen passivated and deuterium passivated Si–SiO₂ interfaces. As hot-carrier degradation is slower in deuterium-annealed MOSFETs, so is the increase of the noise in these devices. The noise-suppressing effect of periodic OFF switching is gradually lost during hot-carrier degradation, as the LF noise under periodic large-signal excitation increases more rapidly than the LF noise in steady-state.     

Electrical noise and RTS fluctuations in advanced CMOS devices

A brief overview of recent issues concerning the low frequency (LF) noise in modern CMOS devices is given. The approaches such as the carrier number and the Hooge mobility fluctuations used for the analysis of the noise sources are presented and illustrated through experimental results obtained on advanced CMOS generations. The use of the LF noise measurements as a characterization tool of large area MOS devices is also discussed. The main physical features of random telegraph signals (RTSs) observed in small area MOS transistors are reviewed. The impact of scaling on the LF noise and RTS fluctuations in CMOS silicon devices is also addressed. Experimental results obtained on 0.18 μm CMOS technologies are used to predicting the trends for the noise figure of foregoing CMOS technologies e.g. 0.1 μm and beyond. The formulation of the thermal noise underlying the LF fluctuations in MOSFETs is recalled for completeness.     

Influence of the sidewall crystal orientation, HfSiO nitridation and TiN metal gate thickness on n-MuGFETs under analog operation

This work characterizes the analog performance of SOI n-MuGFETs with HfSiO gate dielectric and TiN metal gate with respect to the influence of the high-k post-nitridation, TiN thickness and device rotation. A thinner TiN metal gate is found favorable for improved analog characteristics showing an increase in intrinsic voltage gain. The devices where the high-k material is subjected to a nitridation step indicated a degradation of the Early voltage (V_EA) values which resulted in a lower voltage gain. The 45° rotated devices have a smaller V_EA than the standard ones when a HfSiO dielectric is used. However, the higher transconductance of these devices, due to the increased mobility in the (1 0 0) sidewall orientation, compensates this V_EA degradation of the voltage gain, keeping it nearly equal to the voltage gain values of the standard devices.     

Accumulation-layer electron mobility in n-channel 4H-SiC MOSFETs

Accumulation-layer electron mobility in n-channel depletion-mode metal oxide semiconductor field effect transistors (MOSFETs) fabricated in 4H-SiC was investigated using Hall-measurements. The accumulation-layer mobility showed a smooth transition from the bulk value (~350 cm²/V-s) in the depletion regime into accumulation (~200 cm²/V-s). In contrast, the field-effect mobility, extracted from the transconductance, was found to be much lower (~27 cm²/V-s), due to the trapping of the field-induced carriers by interface states. Though the current in depletion/accumulation-mode MOSFETs can be high due to the contribution of bulk conduction resulting in low on-resistance, carrier trapping will cause the transconductance to be low in the accumulation regime     

Technique to improve linearity of transconductor with bias offset voltages controlling a tail current

Considering mobility degradation, a transfer characteristic of the transconductor using bias offset technique becomes nonlinear. Proposed is a technique to cancel the nonlinearity controlling a tail current. Using the proposed technique, the transconductance error is improved to 1/50 of that of the conventional circuit.     

Relationship between MOSFET degradation and hot-electron-induced interface-state generation

Device degradation due to hot-electron injection in n-channel MOSFET's is mainly caused by mobility degradation and reduced mobile charges in the channel introduced by interface-state generation. With the use of simple gradual-channel approximation (GCA), a linear relationship is derived between the threshold shift, relative transconductance reduction, and the number of interface states generated. This model provides a link between the electrical characteristics of a degraded device and its physical damages and, therefore, is a vital tool in the study of hot-electron-induced device degradation mechanisms.     

Hole confinement and low-frequency noise in SiGe pFETs onsilicon-on-sapphire

We present the dc, ac, and low-frequency noise characteristics of SiGe channel pFETs on silicon-on-sapphire (SOS). The SiGe pFETs show higher mobility, transconductance, and cutoff frequency compared to the Si control devices. A significant reduction in low-frequency (1/f) noise is observed in the SiGe pFETs, and understood to be the result of a lower border trap density sampled at the Fermi-level due to the valence band offset. The linear g_m of the SiGe pFET's at 85 K shows a secondary peak which is attributed to the turn-on of the surface channel     

Multiple-channel GaAs/AlGaAs high electron mobility transistors

Multiple-channel high electron mobility transistors (HEMT's) have been designed and fabricated on GaAs/AlGaAs heterostructural material grown by molecular beam epitaxy (MBE). The sheet carrier density of the two-dimensional electron gas (2-DEG) measured at 77 K was linearly proportional to the number of high mobility electron channels, and reached 5.3 × 10¹²cm^-2for six-channel HEMT structures. Depletion-mode devices of the double-heterojunction HEMT were operated between negative pinchoff voltage and forward-biased gate voltage without any transconductance degradation. A peak extrinsic transconductance of 360 mS/mm at 300 K and 550 mS/mm at 77 K has been measured for a 1-µm gate-length double-heterojunction enhancement-mode device. An extremely high drain current of 800 mA/mm with a gate-to-drain avalanche breakdown voltage of 9 V was measured on six-channel devices.     

DC and RF Characteristics of 0.15 pm Power Metamorphic HEMTs

DC and RF characteristics of 0.15 °m GaAs power metamorphic high electron mobility transistors (MHEMT) have been investigated. The 0.15 °m ° 100 °m MHEMT device shows a drain saturation current of 480 mA/mm, an extrinsic transconductance of 830 mS/mm, and a threshold voltage of ‐0.65 V. Uniformities of the threshold voltage and the maximum extrinsic transconductance across a 4‐inch wafer were 8.3% and 5.1%, respectively. The obtained cut‐off frequency and maximum frequency of oscillation are 141 GHz and 243 GHz, respectively. The 8 ° 50 °m MHEMT device shows 33.2% power‐added efficiency, an 18.1 dB power gain, and a 28.2 mW output power. A very low minimum noise figure of 0.79 dB and an associated gain of 10.56 dB at 26 GHz are obtained for the power MHEMT with an indium content of 53% in the InGaAs channel. This excellent noise characteristic is attributed to the drastic reduction of gate resistance by the T‐shaped gate with a wide head and improved device performance. This power MHEMT technology can be used toward 77 GHz band applications.